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Minor tightening and some new constants (no algo changes)

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git-svn-id: https://zxing.googlecode.com/svn/trunk@1969 59b500cc-1b3d-0410-9834-0bbf25fbcc57
This commit is contained in:
srowen 2011-10-14 07:47:05 +00:00
parent a75bc5d021
commit 359551d6e7
1 changed files with 47 additions and 39 deletions
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86
core/src/com/google/zxing/common/HybridBinarizer.java
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@ -41,9 +41,12 @@ public final class HybridBinarizer extends GlobalHistogramBinarizer {
// This class uses 5x5 blocks to compute local luminance, where each block is 8x8 pixels.
// So this is the smallest dimension in each axis we can accept.
private static final int MINIMUM_DIMENSION = 40;
private static final int BLOCK_SIZE_POWER = 3;
private static final int BLOCK_SIZE = 1 << BLOCK_SIZE_POWER;
private static final int BLOCK_SIZE_MASK = BLOCK_SIZE - 1;
private static final int MINIMUM_DIMENSION = BLOCK_SIZE * 5;
private BitMatrix matrix = null;
private BitMatrix matrix;
public HybridBinarizer(LuminanceSource source) {
super(source);
@ -61,12 +64,12 @@ public final class HybridBinarizer extends GlobalHistogramBinarizer {
byte[] luminances = source.getMatrix();
int width = source.getWidth();
int height = source.getHeight();
int subWidth = width >> 3;
if ((width & 0x07) != 0) {
int subWidth = width >> BLOCK_SIZE_POWER;
if ((width & BLOCK_SIZE_MASK) != 0) {
subWidth++;
}
int subHeight = height >> 3;
if ((height & 0x07) != 0) {
int subHeight = height >> BLOCK_SIZE_POWER;
if ((height & BLOCK_SIZE_MASK) != 0) {
subHeight++;
}
int[][] blackPoints = calculateBlackPoints(luminances, subWidth, subHeight, width, height);
@ -88,17 +91,22 @@ public final class HybridBinarizer extends GlobalHistogramBinarizer {
// For each 8x8 block in the image, calculate the average black point using a 5x5 grid
// of the blocks around it. Also handles the corner cases (fractional blocks are computed based
// on the last 8 pixels in the row/column which are also used in the previous block).
private static void calculateThresholdForBlock(byte[] luminances, int subWidth, int subHeight,
int width, int height, int[][] blackPoints, BitMatrix matrix) {
private static void calculateThresholdForBlock(byte[] luminances,
int subWidth,
int subHeight,
int width,
int height,
int[][] blackPoints,
BitMatrix matrix) {
for (int y = 0; y < subHeight; y++) {
int yoffset = y << 3;
if ((yoffset + 8) >= height) {
yoffset = height - 8;
int yoffset = y << BLOCK_SIZE_POWER;
if ((yoffset + BLOCK_SIZE) >= height) {
yoffset = height - BLOCK_SIZE;
}
for (int x = 0; x < subWidth; x++) {
int xoffset = x << 3;
if ((xoffset + 8) >= width) {
xoffset = width - 8;
int xoffset = x << BLOCK_SIZE_POWER;
if ((xoffset + BLOCK_SIZE) >= width) {
xoffset = width - BLOCK_SIZE;
}
int left = x > 1 ? x : 2;
left = left < subWidth - 2 ? left : subWidth - 3;
@ -107,11 +115,7 @@ public final class HybridBinarizer extends GlobalHistogramBinarizer {
int sum = 0;
for (int z = -2; z <= 2; z++) {
int[] blackRow = blackPoints[top + z];
sum += blackRow[left - 2];
sum += blackRow[left - 1];
sum += blackRow[left];
sum += blackRow[left + 1];
sum += blackRow[left + 2];
sum += blackRow[left - 2] + blackRow[left - 1] + blackRow[left] + blackRow[left + 1] + blackRow[left + 2];
}
int average = sum / 25;
threshold8x8Block(luminances, xoffset, yoffset, average, width, matrix);
@ -120,13 +124,15 @@ public final class HybridBinarizer extends GlobalHistogramBinarizer {
}
// Applies a single threshold to an 8x8 block of pixels.
private static void threshold8x8Block(byte[] luminances, int xoffset, int yoffset, int threshold,
int stride, BitMatrix matrix) {
for (int y = 0; y < 8; y++) {
int offset = (yoffset + y) * stride + xoffset;
for (int x = 0; x < 8; x++) {
int pixel = luminances[offset + x] & 0xff;
if (pixel < threshold) {
private static void threshold8x8Block(byte[] luminances,
int xoffset,
int yoffset,
int threshold,
int stride,
BitMatrix matrix) {
for (int y = 0, offset = yoffset * stride + xoffset; y < BLOCK_SIZE; y++, offset += stride) {
for (int x = 0; x < BLOCK_SIZE; x++) {
if ((luminances[offset + x] & 0xFF) < threshold) {
matrix.set(xoffset + x, yoffset + y);
}
}
@ -134,26 +140,28 @@ public final class HybridBinarizer extends GlobalHistogramBinarizer {
}
// Calculates a single black point for each 8x8 block of pixels and saves it away.
private static int[][] calculateBlackPoints(byte[] luminances, int subWidth, int subHeight,
int width, int height) {
private static int[][] calculateBlackPoints(byte[] luminances,
int subWidth,
int subHeight,
int width,
int height) {
int[][] blackPoints = new int[subHeight][subWidth];
for (int y = 0; y < subHeight; y++) {
int yoffset = y << 3;
if ((yoffset + 8) >= height) {
yoffset = height - 8;
int yoffset = y << BLOCK_SIZE_POWER;
if ((yoffset + BLOCK_SIZE) >= height) {
yoffset = height - BLOCK_SIZE;
}
for (int x = 0; x < subWidth; x++) {
int xoffset = x << 3;
if ((xoffset + 8) >= width) {
xoffset = width - 8;
int xoffset = x << BLOCK_SIZE_POWER;
if ((xoffset + BLOCK_SIZE) >= width) {
xoffset = width - BLOCK_SIZE;
}
int sum = 0;
int min = 255;
int min = 0xFF;
int max = 0;
for (int yy = 0; yy < 8; yy++) {
int offset = (yoffset + yy) * width + xoffset;
for (int xx = 0; xx < 8; xx++) {
int pixel = luminances[offset + xx] & 0xff;
for (int yy = 0, offset = yoffset * width + xoffset; yy < BLOCK_SIZE; yy++, offset += width) {
for (int xx = 0; xx < BLOCK_SIZE; xx++) {
int pixel = luminances[offset + xx] & 0xFF;
sum += pixel;
if (pixel < min) {
min = pixel;